Hacker News Reader

Comment by jfm3 | Hacker News Reader

>I'm not sure what massive win for macros is left.

From my point of view, not being able to define new syntax is as serious a limitation as not being able to define new functions, or data structures.

There are a number of specific examples usually cited to explain why the ability to define new syntax is important. Answering these specific examples by adding more static syntax to the language seems to be severely missing the point, to me.

Imagine it was functions instead. "Well your language already has a sort() function, but say you want to use an in-place sort instead of what you get with the standard library? You need the ability to define your own functions." "No we don't, our BDFL added an in_place_sort() routine to the standard library for the next version of the language." That doesn't make sense to me at all.

View on HN

From my point of view, not being able to define new syntax is as serious a limitation as not being able to define new functions, or data structures.

There's a pretty big difference. Both are about DRY. But functions are about abstracting functionality. Macros are about abstracting syntax. Both are useful and can reduce repitition, but in the general dev community, I don't think its clear that everyone is bought into abstracting syntax too much.

For example, the far more mundane operator overloading debates were about just the topic and the side arguing that not all syntax should be abstracted largely won. This is one reason that despite the fact that Lisp is one of the oldest programming languages and easiest to learn, it has never caught on in a big way. It tends to optimize for that which a lot of people don't want optimization.

> [...] in the general dev community, I don't think its clear that everyone is > bought into abstracting syntax too much. [...]

This seems like you're saying "python is better because it does the things people like and doesn't do the things they don't like". But the same argument could be used to claim Microsoft Windows is a great operating system, and that Justin Bieber is a great musician.

> Lisp [...] has never caught on in a big way [...]

This is factually incorrect. Scaled for the size of the industry, it was at one time as popular as Java was a few years ago. What happened then is well documented elsewhere. Search for "ai winter" and "worse is better" to start.

First, I'm not making any claims that Python is better/worse. I'm simply stating that I think many devs (but certainly not all -- and probably even fewer exceptional devs), did not buy into a large degree of syntax abstraction. I personally like some it, but there certainly are limits.

This is factually incorrect. Scaled for the size of the industry,

Sure, if you scale for the size of the industry which found it useful. But that seems nearly tautological.

Okay, then I agree. Lispers use macros sparingly. But not having them at all pinches me terribly and I wish I could explain that better. Decorators don't help much with that pinching :)

I mean the size of the industry that programmed computers at all, not the size of the industry that programmed in Lisp.

"From my point of view, not being able to define new syntax is as serious a limitation as not being able to define new functions, or data structures."

Which is exactly my point. We've gone from "Well, I can use it to define a ternary operator" or "I can use it to define a 'with' block" or "I can create continuations" or a number of other specific examples to "Uh, well, I just like them, here I do this with them" and in my experience there's always an easy "Well, the Pythonic way to do that is this and it's not all that much harder, may even be easier, and is a standard part of a relatively simple language rather than your own hand-rolled thing".

It's a very different argument than it was ten years ago when I first got into Python. It's gone from really strong pro-macro points to personal opinion. I respect and acknowledge that opinion, no sarcasm. But it's not the same.

Your last paragraph isn't relevant to me because the specificity of your example is misleading. It's really hard to come up with an actual macro use case that is not covered by modern Python and is still actually a good idea. (It's trivial to come up with bad uses of macros not covered by Python, but I'm hardly crying about that.)

> It's really hard to come up with an actual macro use case that is not covered by modern Python and is still actually a good idea.

sqlalchemy (and now mongoalchemy) is begging for macros. See CLSQL for an answer.

Regular expressions are infinitely more readable as expressions in a dynamic syntax. See the rx package in Emacs for starters.

What if you want shell/Ruby style back quotes, which in essence create a closure that runs a batch job? See my SHELLSHOCK library (jfm3.org) for the Common Lisp extension. It's not much code at all.

What if you want large literal strings which respect the indentation of their surrounding code, without uglying things up with <<<EOF ? See my BOXEN library (also jfm3.org) for that Common Lisp extension.

What if you want something like Python's r"string", but you want more control over which things are escaped and which are not? See CL-INTERPOL for that.

What if you want anaphora in your control structures?

What if you want Lex/Yacc style parser generator specifications where the type of productions is extensible, and the productions themselves can be generated dynamically at compile time? (This will make no sense to you unless you've ever had no choice but to run m4 on your .l and .y files.)

I could go on. It's not hard for me.

Reply on news.ycombinator.com